Achieving proficiency in core foundational oral language (OL), reading, and writing skills remains difficult for students with specific learning disabilities (SLD) and foundational OL difficulty (National Center for Educational Statistics, 2022). Despite evidence linking OL skills in grammar (morphosyntax, syntax) and vocabulary (semantics) to writing quality (Dockrell et al., 2014, 2015; Kim et al., 2011, 2014, 2015; Kim & Park, 2019; Kim & Graham, 2022; Kim & Schattschneider, 2017) and a high co-occurrence of OL difficulty and SLD (Adlof & Hogan, 2018; Graham et al., 2020) OL difficulties remain under-identified (Adlof & Hogan, 2018; Georgan et al., 2023). To improve identification of these language-based learning disabilities, school-based practitioners must adopt a comprehensive, cascading levels of language assessment approach that examines linguistic skills across modalities (i.e., oral, written), domains (i.e., phonology, morphology, syntax, semantics, pragmatics), and levels (i.e., word-, sentence-, discourse-level) (Berninger et al., 2015). To support comprehensive oral and written language assessment, Reno and McMaster (2024) applied metrics from language sample analysis (LSA) as a complementary scoring mechanism for sentence-level picture-word writing curriculum-based measures (PW CBM-W) that provide discrete estimates underlying syntactic and semantic skills not possible with current CBM-W metrics (Dockrell et al., 2014). Three metrics, mean length of T-Unit in words, mean length of T-Unit in morphemes (MLTU-M), and number of different words (NDW) showed evidence of adequate reliability, criterion-related validity, and sensitivity to growth in a group of typically developing first through third graders. However, the extent to which complementary PW CBM-W and LSA scoring mechanisms exhibit technical quality in students with writing difficulties is unknown. The purpose of this dissertation was to determine the technical quality of complementary PW CBM-W and LSA scoring mechanisms in 123 first through third graders with writing difficulties. Using descriptive statistics, Pearson product-moment correlations, and Spearman's correlations, I determined that two LSA metrics showed evidence of adequate reliability and criterion-related validity with existing CBM-W metrics and the Kaufman Test of Educational Achievement, Third Edition Written Expression subtest (Kaufman & Kaufman, 2014): MLTU-M, using the mean score of two PW CBM-W forms, and NDW, by individual form or the mean of two PW CBM-W forms. Results support research on the role of foundational OL skills in writing (Kim & Graham, 2022) and offer a promising method to support comprehensive sentence-level written language assessment. Future research in PW CBM-W and LSA should investigate sensitivity to growth and identification accuracy for language-based learning disabilities, technical quality with bilingual and emergent bilingual populations, and school-based practitioners' experiences with PW CBM-W and LSA scoring mechanisms as a feasible and acceptable practice. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]